Multiphysics modeling of microwave heating of solid samples in rotary lifting motion in a rectangular multi-mode cavity

Making samples moving during microwave heating is popular way to improve the heating uniformity. However, the common methods, e.g. using turntable and conveyor belt, can only make samples move in one plane, resulting in limited effect on improving the heating uniformity. In order to improve the uniformity of microwave heating in both horizontal and vertical directions, a rotary lifting turntable is used to drive the sample to rotate and lift during heating in this work. To observe the improvement of heating uniformity caused by the rotary lifting motion, an algorithm based on level set methods and implicit function are used to model the process. The electromagnetic field distribution during the heating process obtained by the model is verified by the discrete locations. The transient-temperature of three points and the spatial temperature profile obtained by the model are verified by the experiments. With this model, the heating effect of samples in rotary lifting motion is compared to that of samples only in rotary or lifting motion. The results show that the heating effect of the samples in rotary lifting motion is better than that of most of the samples in static state and single motion mode. In addition, influences of rotating speed, lifting speed, sample properties, and diameter of spiral motion on the heating effect is also analyzed. Since the proposed motion mode is aimed to change the horizontal and vertical position of the sample in the electromagnetic field to make the sample absorb microwave uniformly in all directions, it can be applied to all kinds of microwave cavities regardless of geometric shapes.

Automated summary

In microwave heating, using a rotary lifting turntable to drive samples rotating and lifting can improve heating uniformity. An algorithm was used to model and experiments were conducted to verify the improvement in heating uniformity. The results showed that samples in rotary lifting motion had better heating effect compared to other motion modes.